This invention relates to devices used for the raising and lowering of heavy cargo containers from transportation vehicles such as semi-trailers.
These devices are useful because they allow the same cargo container to be transported by different vehicles. These devices can also be used to remove a cargo container from a container transportation vehicle so that the contents of the cargo container can be loaded efficiently; the tractor of the vehicle does not have to stand idle during the loading or unloading process.
Massive and expensive cranes have been developed for loading and unloading containers from various types of transportation vehicles. These cranes are usually permanently mounted on a foundation and cannot therefore be easily transported to another site.
Accordingly, there is a need for a container handling assembly which is relatively inexpensive to manufacture, and can also be portable.
U.S. Pat. No. 2,069,236 (Fitch) relates to a mechanism for raising and supporting demountable bodies. Fitch discloses a plurality of individual jacks which are mounted at each corner of a container and, through linkage mechanisms, are used to raise the corners of the container. U.S. Pat. No. 3,749,363 (Hauser) relates to jacks for use with containerized cargoes. Hauser discloses the use of individual mobile jacks which can be installed at each corner of a container and, when extended, the container can be lifted.
Other patents of general interest are U.S. Pat. Nos. 4,549,842 (Tidmarsh), 2,643,856 (Sales) and 634,404 (Drinkwater). While some prior art devices are relatively light weight and portable, they can be relatively unstable when handling heavy containers. In addition, none of the prior art devices appear to disclose the use of weight monitoring devices to monitor the weight of the container being handled.